AN EXACT METHOD FOR THE FREE VIBRATION ANALYSIS OF TIMOSHENKO-KELVIN BEAMS WITH OSCILLATORS

In this paper, a modern exact method is proposed for solving the problem of free vibrations of a Timoshenko-type viscoelastic beam with discrete rigid bodies, connected to the beam by means of viscoelastic constraints. The phenomenon of free vibrations of this discrete-continuous system is described by a set of three partial and two subsystem ordinary differential equations with generalized boundary conditions and initial conditions. Vector notation of the equations allows one to identify the self-adjoint linear operators of inertia, stiffness and damping. In this case, these operators are not homothetic hence a separation of variables in this set of equations is possible only in a complex Hilbert space. Such separation of variables leads to ordinary differential equations of motion with respect to time as well as to a set of three ordinary differential equations with respect to a spatial variable and two subsystem algebraical equations. Solution of the boundary-value problem was carried out in the classical way, but its results are complex conjugated. Using these results and the fundamental principle, describing the orthogonality property of complex eigenvectors, the problem of free vibrations of the system with arbitrary initial conditions has been finally solved exactly.     

一种有效的色散补偿镜优化设计方法

介绍了一种有效的色散补偿镜优化设计方法.这种方法将广义模拟退火法和最小二乘法结合起来使用.在色散补偿镜的设计过程中,用双啁啾结构作为初始膜系,发现了一些设计双啁啾结构应注意的规律.这种新的优化方法避免了局部陷阱问题,最终结果也比较令人满意.此外,这种优化设计方法还可以应用于设计啁啾光纤光栅.     

搅拌器内部流动的无网格法三维数值模拟

本文将移动粒子半隐式法(MPS)的基本算法由二维扩展至三维。将圆柱坐标系引入到初场粒子的布置中,避免了在笛卡儿坐标系下处理不规则形状(如斜边或曲边)问题时粒子初场布置困难和精确度较低的问题,改善了对计算边界条件表达的精确性。引入移动边界模型,对直叶片搅拌器的内部流动进行了三维数值模拟。还提出了一种新的初始粒子布置简易方法,明显简化粒子初始布置时的复杂程度,提高了对三维复杂几何形状问题的可操作性。     

一种求解对流扩散问题的高精度无网格方法

无网格局部Petrov-Galerkin方法是近十年发展起来的一种新的数值计算方法,该方法在计算区域内布置一些离散的节点,并利用这些节点构建捕值函数.本文以Smith-Hutton问题为例,把该方法的计算结果与有限容积法高阶格式的计算结果进行比较.研究结果表明:该方法是一种高精度的数值计算方法,能有效地计算高Pe数的流动问题.     

ICP—AES法测定锌及其化合物中的杂质元素

采用样品溶解后直接测定及氢氧化钇共沉淀将锌与被测杂质元素分离后测定相结合，研究了锌及其化合物中Ａｇ，Ｃｏ，Ａｌ，Ｎｉ，Ｆｅ，Ｃｕ，Ｃｄ，Ｃｒ，Ｍｎ，Ｉｎ，Ａｓ，Ｐｂ，Ｓｎ，Ｓｂ，Ｂｉ等１５个杂质元素的ＩＣＰ－ＡＥＳ测定方法，相对标准偏差１．６－８．１％。     

确定D集合的方法

本文讨论了求[1]中所定义的D集合的方法,特别是对最有实用意义的[2]中所定义的D集合,给出了一种高效求找方法,并给出了该方法的理论依据及其实施步骤。讨论了δ(P_i^s_i)(i=1,2,…,K)之间的一些关系性质。最后给出例子说明。     

铝棒振动波动实验的理论分析

结合实际从理论上分析和解释了铝棒振动波动的实验，并揭示出两端自由的金属棒内部的振动传播规律。     

一种有效的量子Monte Carlo模拟方法及其关于二维反铁磁Heisenberg模型的研究

提出一种关于二维反铁磁Heisenberg模型(AFMH)的Monte Carlo模拟新方法。该方法避免了对于相应三维经典自旋系统作模拟计算时的禁态问题和阻错困难。研究还表明,该方法在整个温度区域内的取样迭代效率高,克服了在连续极限下的临界慢化现象,使之能够在更低的温度下进行AFMH的数值研究。     

受迫振动演示实验装置

本文叙述用示波器显示来演示受迫振动的实验装置，可直观地向学生展示受迫振动的幅频特性和相频特性。     

隐式间断有限元方法的参数化边界修正

本文采用并行任意阶精度隐式格式的间断有限元方法,求解来流马赫数为0.01的低速可压缩无黏流动,为增强间断有限元对网格的适应性,采用参数化的方法同时对曲线边界上的积分点位置及外法向向量进行修正,计算结果表明在不做预处理的情况下,隐式间断有限元方法也能较好的计算低速流动,本文所做的参数化边界修正方法有助于间断有限元方法使用通用非结构网格进行高精度的计算.     

离子束-等离子体系统中的参量不稳定性

本文研究了外pump电场E_0在离子束-等离子体系统中所激发的静电低频参量不稳定性。导出了这种低频波的一般色散关系,并用数值方法分析了一维质子束-等离子体系统的参量不稳定性的激发过程。结果表明:离子束对等离子体中参量不稳定性的激发有极重要的影响。当没有离子束时,只能激发一种模式的波;一旦将离子束引入等离子体中,就可以在系统中激发两个波长较长的低频波。     

基波激励和次谐波激励参量放大器特性的分析

本文主要结果有三:第一,推导出基波激励和次谐波激励参量放大器的优值、功率增益、和通带等主要特性,并就这些特性对基波激励源的和次谐波激励源的参量放大器进行比较;第二,通过半导体二极管非线性电容的谐波分量的分析,在激励电压、偏压和放大器的特性间得出定量关系,并且对给定放大器特性求出激励源幅度和频率的稳定要求;第三,推导出放大器的有效噪声,并给出最低有效噪声的设计条件。以上特性的探讨和二极管损耗、信号迴路和镜象迴路通带比、匹配等因子结合在一起进行,使所得结果更具有实际意义。最后举出一数字例子,说明应用本文结果来设计参量放大器的一种可能步骤。 关键词：     

THE DYNAMIC STIFFNESS MATRIX METHOD IN FORCED VIBRATION ANALYSIS OF MULTIPLE-CRACKED BEAM

The dynamic behaviour of a beam with numerous transverse cracks is studied. Based on the equivalent rotational spring model of crack and the transfer matrix for beam, the dynamic stiffness matrix method has been developed for spectral analysis of forced vibration of a multiple cracked beam. As a particular case, when the excitation frequency is close to zero, the solution for static response of beam with an arbitrary number of cracks has been obtained exactly in an analytical form. In general case, the effect of crack number and depth on the dynamic response of beam was analyzed numerically.     

一个用于肿瘤研究中灌流和扩散成像参数分析的应用软件

A software package has been developed to process perfusion, relaxation times and diffusion MRI dat a acquired in cancer research. This software package was written on MATLAB platf orm (Version 6.0). Parameter maps, such as permeability, apparent diffusion coef ficient and T₁ were generated from original MRI data. The features of para metric analysis include ROI analysis, contrast adjust, statistical information generat ion, false color image and zoom in display. Since it was written in Matlab fun ct ions, this package can be used on almost all operation systems (Microsoft window s, Unix, Mac OS & Linux) and it is easy to expand the features.     

A NEW METHOD FOR IN-PLANE VIBRATION ANALYSIS OF CIRCULAR RINGS WITH WIDELY DISTRIBUTED DEVIATION

A new analytical method was developed to predict the in-plane mode shapes and the natural frequencies of a ring with widely distributed deviation. The Laplace transform was used to find the exact solution of eigenvalue problem without assuming any trial functions and finite elements. The widely distributed deviation was effectively formulated in the theory using Gauss-Legendre quadrature. The validity of the proposed method was examined through finite element analysis and modal test. The effects of partial change of the density, the stiffness, and the thickness on the natural frequencies of the ring were investigated.     

方位伺服系统扭转振动固有频率的分析

本文阐述了伺服系统结构设计中估算系统固有频率的必要性,介绍了一种分析和计算经纬仪方位伺服系统扭转振动固有频率的方法。     

计算线源声参量阵辐射场的新方法

本文提出一种计算惠更斯积分的新方法,并利用它来研究线源声参量阵。首先将点源函数展开为一个算符对平面波函数的运算,经过计算证明,如果将这个算符对参量阵远场解进行运算,得到的结果即为线源参量阵辐射场的解。其次证明,参量阵的夫琅和费远场解及菲涅耳修正解都可由本文导出,并且证明,菲涅耳修正只是对半束宽角以外的场有贡献。本文还计算了截断参量阵的辐射场,结果表明,这种阵的近场指向性随距离的减小而变尖锐。并且可以预料,实际参量阵辐射场的性质取决于下述三个场参量:kRsin²θ,βR和R_{1 关键词：}     

固态磁共振中提高四极核检测灵敏度的有效方法

提出用多个单脉冲来激发四极核的磁共振信号，可以显著地提高谱线的信噪比，并对该方法在核磁共振与核四极共振中的应用详细地进行了讨论。 关键词：     

SENSITIVITY ANALYSIS AS A METHOD OF ABSORBER TUNING FOR REDUCTION OF STEADY STATE RESPONSE OF LINEAR PARAMETRIC SYSTEMS

The aim of this paper is to determine whether one dynamic absorber can reduce the amplitude of the steady state vibration of a parametric system for natural and parametric resonance frequencies simultaneously. The efficiency of both the conventional dynamic absorber and the parametric absorber is analyzed. The first order sensitivity analysis of parametric periodic systems in the time domain is applied to obtain logarithmic sensitivity functions in the frequency domain. The first order sensitivity logarithmic functions are used to tune the conventional absorber and the parametric absorber.